Craig Roothoff's H. C. Bay expression system is probably the early
additive one I whimsically called the "A" type.  There were apparently
few of these made, or perhaps they just didn't survive, as I have heard
of only a few of them.  They were designed to play Imperial Automatic
Electric rolls that had additive coding.  Unfortunately rolls were
issued with the same numbers that had either the additive coding or
the 5-step, but with no differentiating marks.

The only way to tell the type of roll is to inspect the expression
coding.  The differences are quite obvious.  The last "A" type roll
was probably made in 1921.  The Cable Company sold its Imperial Roll
operation to QRS in 1922.  QRS issued only 5-step coded rolls until
1926.

In a couple of H. C. Bay Recordo expression systems I tested they
appeared to top out at about level 12 of 16, and the roll expression
coding seemed to do the same.  The system would work with 5-step coded
rolls, though poorly.  I suspect the design was an attempt to work with
both roll types.  The late 16-step rolls would play on the H. C. Bay
system with additive effects, but not very well.

In 1925 QRS acquired the Artrio Angelus roll operation, and in
1926 began issuing a new series of Recordo expression rolls using
the 16-step system.  These rolls were at first all classical titles
from the Artrio Angelus library, and prefixed with the letter "A".
I believe the first were issued under the Aria Divina label, but later
were also issued under the QRS label.  Popular music roll numbers in
1926 were prefixed with "M", and were all 5-step coded at first.  By
1927 some popular  rolls were coded to sound reasonably well on either
type of system, but were all prefixed with "M".

After about 1928 the "A" series was discontinued.  QRS continued to
issue the "M" series with the composite coding for another year or so,
mostly on the longer Dinner Music series, but eventually reverted to
all 5-step coding.  Confusing matters more, QRS later re-issued rolls
from the "A" series prefixed with "M", still coded for the 16-step
system.  This continued until well into the 1960s.  Identifying 16-step
or 5-step rolls can only be done by inspection of the expression coding
if there is no "A" prefix.

A few other companies made 16-step Recordo rolls, but only for a few
years.  The U. S. Auto-Art series was well coded, as was the Wurlitzer
Treasure Chest of Music series.  QRS continued to make 16-step rolls
for Wurlitzer into the early 1930s.  That was the last of them.

Bob Billings
Reno, Nevada